1. Field of the Invention
The present invention relates to a check valve which is to be attached to a fluid apparatus such as a reciprocating pump to prevent fluid from reversely flowing, thereby allowing the fluid to flow only in one direction.
2. Description of the Prior Art
In a reciprocating pump which is used for circulating or transporting chemical cleaning liquids in a semiconductor producing apparatus, for example, a check valve for sucking or discharging the transported liquid is attached. Such check valves include a valve of the gravity type in which closure is attained only by the weight of a valve element itself, and that of the spring type in which a valve element and a compression coil spring for urging the valve element so that the valve element is closely contacted with a valve seat are incorporated into a valve casing. A valve of the spring type is mainly employed because it is superior in sealing property than that of the gravity type (for example, Japanese Patent
Application Laid-Open No. 3-179184 and Japanese Patent Application Laid-Open No. 10-196521).
In such a check valve of the spring type, the valve element and the compression coil spring are independently formed so to be separable from each other, and, during operation of the valve, the center axis of the compression coil spring therefore easily deviates with respect to that of the valve element. In the worst case, the valve element and the compression coil spring are nearly disengaged from each other. Therefore, the urging force exerted by the compression coil spring cannot adequately act on the valve element, thereby often producing a problem in that correct sealing performance due to the valve element is lowered or lost.
The present invention provides a solution to this problem. It is an object of the present invention to provide a check valve of the spring type in which correct sealing performance due to the valve element can be always ensured, and the work of incorporating the check valve into a fluid apparatus such as a reciprocating pump can be efficiently conducted.
The check valve of the present invention is configured by integrally forming a valve element and a compression coil spring which urges the valve element in a valve closing direction, by a metal or a synthetic resin.
In the check valve of the present invention, more specifically, the valve element is formed into a tapered truncated conical shape, the compression coil spring is formed into a cylindrical shape, and the valve element and the compression coil spring are integrally molded into a shape in which the valve element and the compression coil spring are connected to each other via a plurality of connecting rods that are integrally formed between a rear end portion of the valve element and a front end portion of the compression coil spring, so that center axes of the valve element and the compression coil spring coincide with each other. In this case, an outer diameter of the compression coil spring may be set to be larger than a maximum outer diameter of the valve element, or the maximum outer diameter of the valve element and the outer diameter of the compression coil spring may be set to be substantially equal to each other.
In the thus configured check valve, the valve element and the compression coil spring which are formed integrally with each other are not positionally deviated or disengaged from each other. Therefore, the urging force exerted by the compression coil spring can always adequately act on the valve element, and it is possible to exert stable sealing performance in which a reverse flow and liquid leakage can be always surely prevented from occurring.
As described above, the check valve of the present invention can always exert stable sealing performance, and is advantageous from the view point of the work of incorporating the check valve into a fluid apparatus such as a reciprocating pump.